Automatic switch for electric heating



B. G. ,C. STEPHENS. AUTOMATIC swncn FOR memo HEATING APPLIANCES.

APPLICATION FILED FEB. [4, I920- Patented July 18, 1922.

BENJAMIN GEORGE CLAUDE STEPHENS, OF AUCKLAND, NEW ZEALAND.

auronerrc swrron non nnnornio im a'rmc arrnrancns.

Specification 01' Letters Patent.

Patented J 1113 18, 1922.

' Application use February 14. 1926. sum in. 858,792.

Toallwhomitma, concern:

Be it known hat I, Benton; Gannon moon STEPHENS, subject of the King of Great" Britain, residing at 208 Victoria'. Arcade, Auckland, in the Dominion of New Zealand, electrical engineer, have invented a I new and useful Automatic Switchfor Electric Heating Appliances; and l do hereby declare the followin to be a full, clean and exact description 0 the semen .j r

This invention has been devisedin order to provide an improved construction ofauto; matic switchior electric hea g appliances. It has designed particular-lyric!" use with electric irons but'it is readily adaptable to other appliances, in which: electricity is the heatin' agenc "Its purpose is toJpro- 'vide for t is elec ric heating circuit; being broken in a positive and effectiveinanncr upon the temperature of. the ap liance reaching a, predetermined 'oint, and t ereby to prevent any danger of re from overheating in the event of the appliance being left with the current on for any lngthhf time.

The adaptation of the invention to electric irons rovides a simple and oflicicnt means where y all dangers from fires occurrin through the iron overheatin are remove The invention consists in t e combination with a iii-metallic strip pensive properties positioned in the appliance so as to be acted on by the heat thereof.

of a switch apparatus of special design that when in position, is held against the act-ion of certain springs to close the heating circuit. This apparatus is also so constructed that it will be engaged by the stri when it moves to a certain extent, under t e action of the heat, and freed so that its springs will force it away and break the circuit.

The invention is herein described in relation to an electric iron and its application thereto is illustrated in the accompanying drawings, in which Figure 1 is a side elevation of an iron, the ordinary plate cover being shown in section in order to illustrate the position of the apparatus.

Figure 2 is a plan thereof, the cover being broken away to show the position of the stri Figure 3 is a cross sectional elevation of the non showing the switch in its closed position.

Fig. 3 is a detail sectional view of the same on a larger scale.

of well known ex- G 1 1 re e is a Ion ltudinnl section of the switc such section ing at right angles to that shown in Figure 8.

Figure 5 isan underneath plan of the switc i. Figure 6 is a plan of a portion of the iron cover showing 1t formed to receive the invention. p Ais the usual sole late of the iron, B'the resistance plateand .the cover secured over them. In this invention a. bi-metallic strip D is arranged'between' the resistance plate and the cover; suchstrip beingmade inhany the approved" Ways governing the'construction of such, forms of thermostatic appliances'. It isfsha. ed with'a horse shoe bend so as to form-a s blli'lfl that is secured to the insideof theoover 0%) the screws d and thus held from movenient "and a long log that extends lo 'tudinnlly beneath the cover and is left iee. The expansion and contraction movement of the strip will therefori'ie' cause a lateral movement of this free en The switch apparatus consists in two contact blocks E E that are arranged in the cover and fastened to an insulated late F that is fixed beneath the cover, so at the blocks project u wards throu h apertures G formed in t e cover for at purpose. A strip H of mica, or the like, overlies the cover top and surrounds the blocks so as to insulate them from one another and the cover. These blocks are arranged in the resistance circuit of the iron so that when they. are unbridged the circuit is broken. Gombined with such contact blocks, is a cap piece J that is adapted to fit over the blocks and to be fastened to the cover by means of a lug; K on one side that hooks into an aperture K on the cover, so as to enga. e beneath its edge, and a spring controlle hasp M that passes into another aperture M on the cover and engages beneath it. The bottom of this hasp is positioned adjacent to the free end of the strip D and its movement to free the cover is in the line of the movement of such free end when the strip expands. A regulating screw D is screwed through the end of the strip and this screw is adapted to engage the hasp and push it away from angagement with the cover, when the strip expands to the predetermined extent fixed by the adjustment of the screw D. This action will free the cap so that it may be lifted from the cover.

Inside the cap is a sprin metallic bridge N that is fastened to one en of a folded leaf spring 0, the other end of which is fastened to the inside of the cap and suitably insulated therefrom. adapted to be placed in strong compression when the cap is placedinposition to cause the bridge to bridge'thecont'act E and E, and to be locked todthe cover, as shewn in Figure 3. Thisfis the; position the switch will retain under ellnormalciroums'tances, the heating circuit completed through the bridging of the contacts. When,:ho\.v ever, the heat reaches such a degreeas. to cause. the strip tohexpand "the necessar amount, its free end Wlll engage and pus back the keep 185, the eby PBrmittin the compressed spring 0' to expand and t ow the cap and bridgecleerof cover and thereby break thecircnitfin the required manner. 7

The circu1t.rv1l1,. then hare to be, manually restored by replacing the-cap, the invention thus .difiering. iILjitS work ng; from. other automatic switches ernplo inggthe thermostatic strip. and in. which. t e, circuit isautomatically restoredon. the lowering of. the temperature to the. normal.

I claim 1. In automatic switches for electricheating a. pliances, the comhi na.tion with embinietallic thermostatic strip arranged within This spring and bridge are- ,adaptedto be engaged and operated by the movement of the bi-metallic strip through its expansion beyond a predetermined extent, substantially as specified.

2. In automatic switches for electric heating appliances, the combination with a. pair of heating circuit contact terminals, of a cap adapted to be fitted over such terminals and to be held in position by a spring has'p, a spring within such cap having a bridge p ece attached thereto and adapted when the cap is in position to be compressed and to .hold the bridge piece across the terminals, and a bi-metal 'c strip arranged within 'the heat influence having one end made fast, and the other free and positioned, adjacent t9;the said hasp so as to engage and free it when the strip expands, snhstantially as specified,

In testimony whereof, I have signedthis specification in the presence of two subscribing witnesses.

BENJAMIN GEORGE CLAUDE STEPHENS. Witnesses:

DAVID BROWN HU'rroN, S. Owrmnn. 

